A tilt position adjustment mechanism is a mechanism for adjusting an inclination angle of the steering wheel to the best driving position according to the body type or preference of the driver. In adjusting the inclination angle of the steering wheel, after the inclination angle of the steering wheel is adjusted steplessly in a state where a tilt clamp mechanism is unclamped once, the tilt clamp mechanism is again clamped.
In the steering device having the steering position adjustment mechanism of this type, a vehicle body attachment bracket is fixed to a vehicle body, and a fastening rod is allowed to insert into a tilt adjustment slender groove and a column of the vehicle body attachment bracket. During tilt clamping, a stationary cam is pressed in an axial direction by a movable cam that rotates due to the operation of an operating lever to fasten the fastening rod, and the column is pressed toward the vehicle body attachment bracket for clamping.
The stationary cam has a cam surface for relatively pressing the movable cam toward the stationary cam in the axial direction, and a locking unit for disabling the stationary cam to be relatively rotated with respect to the movable cam, and for sliding along the tilt adjustment slender groove at the time of adjusting the tilt position. Accordingly, the stationary cam requires both characteristics of durability for allowing a cam surface to withstand a large clamp force, and an impact reduction capability for reducing an impact sound when the locking unit is abutted against the tilt adjustment slender groove at an adjustment end of the tilt position.
The stationary cam of the steering device disclosed in Patent document 1 integrally couples two parts consisting of a cam member having a cam surface made of a high-hardness material and a locking unit made of a synthetic resin to provide those characteristics described above.
Also, in the steering device having the steering position adjustment mechanism of this type, when the fastening force of the fastening rod is lax, the column is caused to move in a tilt direction during a secondary collision where a driver collides with the steering wheel, resulting in a risk that an air bag disposed in the steering wheel cannot accept an occupant at an effective position.
As a mechanism for blocking the movement of the column during this secondary collision, there is a tilt lock mechanism in which a stationary tilt lock gear is disposed on the vehicle body attachment bracket side, and a movable tilt lock gear the is engaged with the stationary tilt lock gear is inserted into the fastening rod.
With this configuration, during the tilt locking, the fastening rod is fastened to engage the movable tilt lock gear with the stationary tilt lock gear, thereby improving a retention force in the tilt direction, with the result that even if an impact load due to the secondary collision is exerted on the steering wheel, the column is not moved in the tilt direction.
In the above steering device that enables the tilt position to be adjusted steplessly, when the fastening rod is fastened to engage the movable tilt lock gear with the stationary tilt lock gear during tilt locking, the respective threads of the movable tilt lock gear and the stationary tilt lock gear may be abutted against each other depending on the tilt position, thereby disabling normal engagement. When the respective threads of the movable tilt lock gear and the stationary tilt lock gear are abutted against each other, the tilt lock becomes insufficient, and when the fastening rod is forcedly fastened, the movable tilt lock gear and the stationary tilt lock gear are strongly rubbed with each other, thereby causing discomfort for the driver.
In order to prevent the respective threads of the movable tilt lock gear and the stationary tilt lock gear from being abutted against each other, there is a need that the movable tilt lock gear is movably fitted onto the stationary cam in the tilt direction, and the movement of the movable tilt lock gear in the tilt direction with respect to the stationary cam is elastically supported by a spring to provide the degree of freedom of a position at which the movable tilt lock gear and the stationary tilt lock gear are engaged with each other.
However, in a structure in which the spring provides the degree of freedom of the position at which the movable tilt lock gear and the stationary tilt lock gear are engaged with each other, because the structure is complicated, and the number of parts increases, a structure easy in assembling is required.